Actin Protofilament Orientation at the Erythrocyte Membrane

Picart, Catherine; Discher, Dennis E.

doi:10.1016/s0006-3495(99)76938-9

Cited by 31 publications

(39 citation statements)

References 44 publications

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“…28,29 Since the resolution of the FPM was within 15 • to 20 • , 28 our predicted θ ≤ 22 • at λ = 1 and 1.03 when K m ≥ 0.2 pN/nm would not be inconsistent with the experimental data. 28,29 In hypotonically sphered erythrocyte ghosts (λ =∼ 1.03), our model does not consider the conformational changes of Sp induced by hypotonicity per se. 26 …”

Section: Protofilaments In "Natural State" and Hypotonically Sphered mentioning

confidence: 57%

“…28,29 It was found that greater than 60% of the protofilaments measured by FPM in both the natural state (λ = 1) and osmotically sphered erythrocyte ghosts 29 (λ ∼ 1.03) 15 had a pitch angle ≤ 22 • , at least within the 15 • to 20 • resolution of current methods. Therefore, these protofilaments were more tangent than normal to the lipid bilayer.…”

Section: Introductionmentioning

confidence: 92%

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3-D Nanomechanics of an Erythrocyte Junctional Complex in Equibiaxial and Anisotropic Deformations

et al. 2005

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The erythrocyte membrane skeleton deforms constantly in circulation, but the mechanics of a junctional complex (JC) in the network is poorly understood. We previously proposed a 3-D mechanical model for a JC (Sung, L. A., and C. Vera. Protofilament and hexagon: A three-dimensional mechanical model for the junctional complex in the erythrocyte membrane skeleton. Ann Biomed Eng 31:1314-1326, 2003) and now developed a mathematical model to compute its equilibrium by dynamic relaxation. We simulated deformations of a single unit in the network to predict the tension of 6 alphabeta spectrin (Sp) (top, middle, and bottom pairs), and the attitude of the actin protofilament [pitch (theta), yaw (phi) and roll (psi) angles]. In equibiaxial deformation, 6 Sp would not begin their first round of "single domain unfolding in cluster" until the extension ratio (lambda) reach approximately 3.6, beyond the maximal sustainable lambda of approximately 2.67. Before Sp unfolds, the protofilament would gradually raise its pointed end away from the membrane, while phi and psi remain almost unchanged. In anisotropic deformation, protofilaments would remain tangent but swing and roll drastically at least once between lambda(i) = 1.0 and approximately 2.8, in a deformation angle- and lambda(i)-dependent fashion. This newly predicted nanomechanics in response to deformations may reveal functional roles previous unseen for a JC, and molecules associated with it, during erythrocyte circulation.

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Section: Protofilaments In "Natural State" and Hypotonically Sphered mentioning

confidence: 57%

Section: Introductionmentioning

confidence: 92%

3-D Nanomechanics of an Erythrocyte Junctional Complex in Equibiaxial and Anisotropic Deformations

et al. 2005

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“…These lie roughly parallel to the membrane plane (620°) and are randomly oriented. 37 There are ;30 000 to 40 000 protofilaments per red cell, with 6 to 8 actin monomers in each of the 2 strands.…”

mentioning

confidence: 99%

Anatomy of the red cell membrane skeleton: unanswered questions

Lux

2016

Blood

298

307

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The red cell membrane skeleton is a pseudohexagonal meshwork of spectrin, actin, protein 4.1R, ankyrin, and actin-associated proteins that laminates the inner membrane surface and attaches to the overlying lipid bilayer via band 3–containing multiprotein complexes at the ankyrin- and actin-binding ends of spectrin. The membrane skeleton strengthens the lipid bilayer and endows the membrane with the durability and flexibility to survive in the circulation. In the 36 years since the first primitive model of the red cell skeleton was proposed, many additional proteins have been discovered, and their structures and interactions have been defined. However, almost nothing is known of the skeleton’s physiology, and myriad questions about its structure remain, including questions concerning the structure of spectrin in situ, the way spectrin and other proteins bind to actin, how the membrane is assembled, the dynamics of the skeleton when the membrane is deformed or perturbed by parasites, the role lipids play, and variations in membrane structure in unique regions like lipid rafts. This knowledge is important because the red cell membrane skeleton is the model for spectrin-based membrane skeletons in all cells, and because defects in the red cell membrane skeleton underlie multiple hemolytic anemias.

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“…Since RBC actin filament subunits exchange via barbed-end dynamics [36], Brownian ratchet forces may be generated where barbed ends within dynamic hotspots face toward the RBC membrane. However, analyses of actin filament orientation within the RBC membrane skeleton [69,70] have not assessed whether barbed or pointed ends are preferentially oriented towards the membrane. In the future, differential fluorescent labeling of barbed vs. pointed filament ends [71] followed by three-dimensional super-resolution imaging [72] of intact cells will enable such an analysis.…”

Section: Dynamic Characteristics Of Rbc Actin Filamentsmentioning

confidence: 99%

Feisty filaments

Gokhin

Fowler

2016

Current Opinion in Hematology

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STRUCTURED ABSTRACT Purpose of review The purpose of this review is to discuss recent advances and unsolved questions in our understanding of actin filament organization and dynamics in the red blood cell (RBC) membrane skeleton, a two-dimensional quasi-hexagonal network consisting of (α1β1)2-spectrin tetramers interconnecting short actin filament-based junctional complexes. Recent findings In contrast to the long-held view that RBC actin filaments are static structures that do not exchange subunits with the cytosol, RBC actin filaments are dynamic structures that undergo subunit exchange and turnover, as evidenced by monomer incorporation experiments with rhodamine-actin and filament disruption experiments with actin-targeting drugs. The malaria-causing parasite, Plasmodium falciparum, co-opts RBC actin dynamics to construct aberrantly branched actin filament networks. Even though RBC actin filaments are dynamic, RBC actin filament lengths are highly uniform (~37 nm). RBC actin filament lengths are thought to be stabilized by the capping proteins, tropomodulin-1 and αβ-adducin, as well as the side-binding protein tropomyosin, present in an equimolar combination of two isoforms, TM5b (Tpm1.9) and TM5NM1 (Tpm3.1). Summary New evidence indicates that RBC actin filaments are not simply passive cytolinkers, but rather dynamic structures whose assembly and disassembly play important roles in RBC membrane function.

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Actin Protofilament Orientation at the Erythrocyte Membrane

Cited by 31 publications

References 44 publications

3-D Nanomechanics of an Erythrocyte Junctional Complex in Equibiaxial and Anisotropic Deformations

3-D Nanomechanics of an Erythrocyte Junctional Complex in Equibiaxial and Anisotropic Deformations

Anatomy of the red cell membrane skeleton: unanswered questions

Feisty filaments

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